1. Field of the Invention
The invention is directed to a device for injecting a liquid into an exhaust gas flow and to an exhaust gas aftertreatment system.
2. Description of the Related Art
It is a characteristic of internal combustion engines operated with heavy oil that the fuel that is used, i.e., the heavy oil, has a high sulfur content. Sulfur oxides can react with other constituents of the exhaust gas and lead to deposits that impair the efficiency of the exhaust gas cleaner.
An internal combustion engine with an exhaust gas turbocharger and an exhaust gas cleaner is known from DE 10 2004 027 593 A1. The exhaust gas turbocharger is constructed either as a one-stage exhaust gas turbocharger or as a two-stage exhaust gas turbocharger. The exhaust gas cleaner comprises a SCR catalyst, which is positioned either downstream of the turbine of the exhaust gas turbocharger or upstream of the turbine of the exhaust gas turbocharger in the one-stage exhaust gas turbocharger. For a two-stage exhaust gas turbocharger, the SCR catalyst is positioned between a high-pressure turbine of a high-pressure exhaust gas turbocharger and a low-pressure turbine of a low-pressure exhaust gas turbocharger.
A SCR catalyst uses ammonia as reductant. In exhaust gas aftertreatment systems known in the art, an aqueous urea solution is injected into the exhaust gas upstream of the SCR catalyst, this aqueous urea solution being decomposed and evaporated in the exhaust gas flow to form water vapor, carbon dioxide and ammonia.
The urea solution is preferably introduced into the exhaust gas flow by an atomizing nozzle, which can be constructed as a one-component nozzle or as a two-component nozzle, DE 10 2009 005 528 A1 discloses an atomizing nozzle designed as a two-component nozzle which serves to introduce a liquid into the exhaust gas flow of an exhaust gas aftertreatment system using pressurized air. The liquid to be atomized in the exhaust gas flow and the pressurized air are first mixed directly upon exiting the two-component nozzle. The liquid to be atomized and the pressurized air are guided separately within the two-component nozzle.